This invention relates to an accumulator for logs of wound paper, such as toilet paper and tissue paper, and, more particularly, to a festoon accumulator which includes a downwardly travelling feed section and a horizontally travelling discharge section.
The desirability of providing an extensible web path between components of equipment in a processing line is well known in the paper processing and converting industry. Devices for extending the path of and accumulating continuous web materials are shown, for example, in U.S. Pat. Nos. 3,796,360 and 4,009,814. Interspaced accumulators accept or discharge excess material whenever there is a speed difference between processing equipment.
Both of these patents show a stationary set of rolls and a second set of rolls movable with respect to the stationary set. Movement away from the stationary set increases the web path and thus accumulates material whenever input speed exceeds output requirements for downstream processing. Whenever output requirements are greater than input, the movable set moves toward the stationary set, this action providing the differential requirement from the accumulated reserve until the reserve is depleted.
In the accumulation of continuous webs, these teachings recognize the importance of having all rolls in the movable set connected to a common member, which assures that all rolls in the movable set will move at the same velocity at the same time. This approach eliminates instantaneously higher tensions that could be introduced if the movable rolls acted independently and sequentially. Depending on tensile strength of the material handled, these patents teach both idling and driven roll sets, the latter being necessary for lightweight low tensile strength webs.
For the storage of discrete articles and, more particularly, for logs of wound material, automatic storage and discharge or surges is also desirable and can be accomplished using a different principle of operation whereby interconnected sprocket pairs move independently until limits of travel are reached, at which time movement is transferred to the next pair in sequence. It is known art for example, that a log accumulator can be used to accumulate and subsequently discharge logs when there is a variation of speed between input and output requirements. One such log accumulator utilizes movable pairs of interconnected sprockets which move up and down between upper and lower sets of stationary sprockets. These interconnected and movable sprocket pairs are arranged to be at the limit of upward travel when conveying logs between processing equipment and when input speed equals or is less than output speed. This configuration dictates the direction of chain movement around the sprockets and precludes vertical downward motion of log carriers at the input station.
One object of this invention is to provide downward motion of the receiving log carriers at the input station, this downward velocity being more nearly equal to the downward velocity component of a log being gravity fed to a carrier. With log loading from a terminal support at the input side, free fall of the log results in the downward velocity component of the log being more nearly equal to the velocity of carrier descent compared to upward carrier movement. This beneficial relationship between the movement of the log and the carrier provides higher loading rates, less space between carriers and consequent greater capacity, a minimal normal transport path, greater reliability of loading with fewer jams, and gentler handling than is obtained with known accumulators.
Another object of the invention is to provide a combination transport-accumulating system in which the discharge section is arranged horizontally to pass over a plurality of discharge points. The normal practice is to dump wound logs into one or more lanes of a log saw which then cuts the logs into discrete roll segments. In some cases, two log saws are required to handle the capacity from a processing line. The horizontal motion of the discharge section simplifies the feeding of a plurality of lanes of a single log saw and provides the capability of feeding more than one saw.
A further object of the invention is to synchronize discharge speed from the accumulator with demand from downstream equipment by providing direct drive from the equipment to the conveyor chain at the discharge end without any intermediate transport or metering devices.